In recent years, more and more automobiles mount drive motors in view of environmental issues. Such a drive motor to be mounted in a car is desired to provide large output power for driving a vehicle and have a small size for car installation. In particular, a hybrid electric car has to mount an engine and a drive motor together in an engine room and thus highly requires a small-sized motor. To enhance the motor power, there have been methods for increasing a cross sectional area of a coil to be used in the motor and also increasing a space factor or lamination factor of a stator. On the other hand, various approaches for reducing the size of a motor have been studied.
As one of the methods for increasing the cross sectional area of the coil of the stator, there is proposed a method for forming a coil by winding a flat rectangular conductor. In a case where the coil made of the flat rectangular conductor having a rectangular cross section is partially inserted in rectangular slots, such a coil can achieve a lower void ratio than a coil made of a conductor having a circular cross section. This can lead to an enhanced lamination factor. It is further found that a stator formed from segment coils each made of a flat rectangular conductor is advantageous to reduce iron loss, copper loss, and so on. However, when a segment coil is to be made of a flat rectangular conductor, a processing method therefor is somewhat hard. It is thus desired to simplify the processing method.
Patent Document 1 discloses a technique for a device for forming a segment to be used for a coil of a rotary electric machine, a method for forming the segment, and the segment made by the method. This device includes a pair of first forming dies for forming a crank section and a curved section of the segment, a pair of second forming dies for forming the crank section and shoulder sections, and two forming rollers for forming the shoulder section in cooperation with the second forming dies. In forming a segment from a flat rectangular conductor, the first forming dies clamp the flat rectangular conductor to form the curved section and the crank section. Then, the second forming dies clamp the flat rectangular conductor to further deform the crank section. Successively, the forming rollers press the flat rectangular conductor against the second forming dies, thereby forming the segment. In this way, the bending work can be realized in consideration of a spring back effect of the flat rectangular conductor.